From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F0DE62949E0; Thu, 6 Aug 2026 13:58:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786024720; cv=none; b=gKh1ZqMSyxpIu06oEynFjuPnqCiqBikff1idPaT7V9iyxlAGvHeUObcl9OZWxSz+J0lT3o0w9armb+MzVz1XnHEqKDeirB8tWwLkH2jATdtAD4aioTM4xnkkLEZPmdRAOPWSyEEASjF+TVp74l4lRkj8k0MntR+Q9YMnlFpmjd0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786024720; c=relaxed/simple; bh=/Pw8u1p6Zi7jNUDoze5GpbNpVFr7BAHkkCNPRnWltLY=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Gsjd5aiaiH0Urf/2AB3aeIMxA4x8m88Hm8rN7pYvqgT2ur/vjJ4HnmjugRQ7qeBLyKBzQrVwDcc40cqw3kelBgjTxxrMR2RbMbitG/ZTRMkUtnVn1BZN1Jl5lw4xBDNncyD8EcN1rnMxGa3j2JXgTLQC7a5uoKcnlq+fdzKguoU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=cfWtjqYf; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="cfWtjqYf" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B44221F000E9; Thu, 6 Aug 2026 13:58:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786024718; bh=9wRO74CcRIalo/k8pD9p1nvIQvOuxyVB7Ax6J3p+LFk=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=cfWtjqYfxsKZVa95uwGYkFOkF4656sllygFEOdMkS+9F6TRD9d2AZvKUYCyl8qOfV RPHyAblmhkJUXr6M22cEm35E1ew9IQJKJWGaVEcVai7iuZM6+FYmS8/jo59S2Q85mD /qMNFhb0QSFM32zF6zBR1Q1N7i8LtbX3YTq2iDRXAXfMy8BNUP9iRgMYDK2aJaTKwR nRAPTyvvG/8lhjbL7SgkSF1+DdKiI8CZUdizWC0vfWBXIDmUQ9JCwtROMOBC36lAQw N6gn/DCSR/u2P5N11sKhZS9nInHhUhymPJVEXPWV7WPUdxYc/dZebKkGn6BtCtRi7N VTgpKbGJJm/hg== Message-ID: Date: Thu, 6 Aug 2026 15:58:29 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH v5 3/4] mm/vmscan: avoid pointless large folio splits without swap To: Xueyuan Chen , akpm@linux-foundation.org, linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, zhaonanzhe@xiaomi.com, baohua@kernel.org, hannes@cmpxchg.org, youngjun.park@lge.com, baolin.wang@linux.alibaba.com, hughd@google.com, chrisl@kernel.org, kasong@tencent.com, shikemeng@huaweicloud.com, nphamcs@gmail.com, baoquan.he@linux.dev, mhocko@kernel.org, roman.gushchin@linux.dev, shakeel.butt@linux.dev, muchun.song@linux.dev, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, qi.zheng@linux.dev, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com References: <20260730122304.2496440-1-xueyuan.chen21@gmail.com> <20260730122304.2496440-4-xueyuan.chen21@gmail.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/30/26 14:23, Xueyuan Chen wrote: > From: "Barry Song (Xiaomi)" > > When swap is disabled, exhausted, or unavailable due to memcg swap > limits, splitting a large anonymous folio cannot make swapout progress. > The fallback only destroys the large folio and inflates split statistics. > > Use -E2BIG from folio_alloc_swap() as the explicit signal that splitting > the folio might allow swapout of smaller pieces. For other allocation > failures, keep the existing activation path and avoid the split. > > This preserves the split fallback for fragmented or partially available > swap, while avoiding it when there is no backing space for any part of the > folio. > > Reported-by: Nanzhe Zhao Do you have a link to the report? I assume this is not Fixes-worthy. > Signed-off-by: Barry Song (Xiaomi) > Signed-off-by: Xueyuan Chen > --- > mm/vmscan.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 26df81e773ff..457049e130df 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -1263,6 +1263,8 @@ static unsigned int shrink_folio_list(struct list_head *folio_list, > */ > if (folio_test_anon(folio) && folio_test_swapbacked(folio) && > !folio_test_swapcache(folio)) { > + int ret; > + > if (!(sc->gfp_mask & __GFP_IO)) > goto keep_locked; > if (folio_maybe_dma_pinned(folio)) > @@ -1281,11 +1283,14 @@ static unsigned int shrink_folio_list(struct list_head *folio_list, > split_folio_to_list(folio, folio_list)) > goto activate_locked; > } > - if (folio_alloc_swap(folio)) { > + ret = folio_alloc_swap(folio); > + if (ret) { > int __maybe_unused order = folio_order(folio); > > if (!folio_test_large(folio)) > goto activate_locked_split; > + if (ret != -E2BIG) > + goto activate_locked; > /* Fallback to swap normal pages */ > if (split_folio_to_list(folio, folio_list)) > goto activate_locked; Acked-by: David Hildenbrand (Arm) -- Cheers, David